China milk crisis forces food testing rethink

China’s baby milk crisis - in which thousands of Chinese babies have developed kidney stones after drinking milk contaminated with melamine, an industrial chemical - has highlighted the need for the country to improve detection standards for chemical contaminants in foods.

’We are working with other government departments to study how to include previously unmonitored compounds when revamping our food quality detection standards,’ Li Changjiang, head of China’s General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ), the food safety watchdog, told a press conference on 17 September.

More than 50,000 babies have reportedly developed kidney problems after drinking the contaminated milk. Four babies have died and 13,000 are in hospital - over 100 of these in a serious condition. Most of the contaminated milk powder was made by Hebei Province-based dairy firm Sanlu Group, which is 43 per cent owned by New Zealand dairy farmers’ group Fonterra. Initial reports suggested that Sanlu was the only company involved but then melamine was detected in milk powder from 22 other dairy firms, although at far lower levels. The chemical was also found in fresh milk products from leading Chinese dairy firms including Inner Mongolia-based Yili Industrial Group and Mengniu and Shanghai-based Bright Dairy. Meanwhile, in Hong Kong, two main supermarket chains were reported to have recalled milk products made by Nestl?, Dutch Lady and Mr Brown, found to contain traces of melamine.

The contamination is believed to have occurred at milk collection centres, where melamine would have been added to boost apparent protein content. Dairy firms judge milk quality largely by protein content, which they estimate from nitrogen levels. Adding melamine (C3H6N6) - a white crystalline chemical used to make plastics, fertilisers and cleaning products - to milk significantly raises nitrogen levels. At high concentrations, the chemical can cause kidney stones and renal failure, particularly in infants. Last year, melamine-contaminated pet food from China sickened or killed thousands of cats and dogs in the United States.

In a nationwide campaign to detect melamine, Chinese dairy firms and the quarantine departments have rushed to buy expensive HPLC (high performance liquid chromatography) machines. But according to Fang Shimin, a Chinese newspaper columnist with a PhD in biochemistry, there are simpler and cheaper ways to detect melamine. For example, trichloroacetic acid can be used to precipitate proteins from milk. The proteins can then be filtered out and any nitrogen in the remaining liquid can be attributed to non-proteinaceous compounds such as melamine. ’We have long known about this simple technique but the food safety authorities have never paid importance to food safety detection so they did not think of adopting it,’ Fang told Chemistry World.

AQSIQ’s Li admits that the food quality monitoring criteria only cover nutritional aspects of food and not forbidden chemical contaminants. Implementing any new standards is a challenge. ’It is impossible for food safety authorities to monitor every product from millions of producers. The key is to punish severely those who contaminate food to ensure producers take responsibility for product safety,’ Ke Bingsheng, president of China Agricultural University, told the Annual Meeting of China Association for Science and Technology in September.